Vibrio vulnificus is a natural inhabitant of coastal waters, including the US Gulf. The bacterium causes rapid septicemia after consumption of contaminated seafood (especially raw oysters), predominantly in persons with liver dysfunction. Among food-bourne pathogens, V. vulnificus is most notable for its high rates of hospitalization and death. Indeed, V. vulnificus accounts for 1% of deaths from food-bourne illness despite causing only 0.003% of illnesses. Attempts by the FDA to protect consumers by implementation of post- harvest processing mandates met with significant resistance from the shellfish harvesting industry forcing the FDA to review its policies. Thus, the study of V. vulnificus pathogenesis has become a food safety and public policy priority. Recent studies establish that cytotoxicity of V. vulnificus is predominantly associated with a large Multifunctional-Autoprocessing RTX toxin (MARTXVv). In this study, we demonstrate that this toxin is directly linked to pathogenesis by the intragastric route of infection. We propose to study the role of the MARTXVv toxin in pathogenesis using in vivo, cell culture, and biochemical systems. The focus of the proposal will be mechanisms directly impacting early infection after consumption of contaminated food and identification and characterization of specific regions of the toxin linked to tissue damage and immune system evasion. PUBLIC HEALTH RELEVANCE: Vibrio vulnificus is a bacterium that inhabits the US Gulf and causes sepsis and necrotizing fasciitis (flesh- eating bacteria). This study of V. vulnificus pathogenesis will specifically characterize a virulence factor secreted by the bacterium that is linked to disease after consumption of contaminated food (especially oysters). When completed, this study will define how this factor contributes to food bourne infection.